Apparatus for degassifying a liquid



Sept. 27, 1966 B. E. STERN ,2

APPARATUS FOR DEGASSIFYING A LIQUID Filed Oct. 8, 1962 38 p 37 33 32 3o 3 '34 23 20 24 v. 6 23 6 3 ,133 2 2% 3 2? m BE/VGT E VERT STERN I/VVENTDR Arm/wars United States Patent 3,274,756 APPARATUS FOR DEGASSIFYING A LIQUID Bengt Evert Stern, Mullingstorp, Kuddby, Sweden Filed Oct. 8, 1962, Ser. No. 229,143 1 Claim. (Cl. 55-182) The present invention relates to a procedure for the analysis of blood gases and an apparatus for use in this procedure.

The determination of the content of various gases in the blood is of major importance in medicine. The gases may consist of respiratory oxygen and carbon dioxide of of anaesthetic agents. It may also be required to know the ratio between the amounts of ordinary water vapour and heavy-water vapour in the blood. It is the oxygen content, however, that is of particular importance.

The usua techniques for determining the oxygen content of the blood are exeremely time-consuming, and large quantities of blood are required.

With the development of gas chromatography the estimation of the oxygen content of the blood has been considerably simplified, and both the time and the quantities required have been much reduced. A rapid technique for such an estimation has been reported which depends upon the liberation of oxygen and carbon dioxide from the blood sample by means of chemicals in aqueous solution. This method has a number of disadvantages; for instance, not all of the oxygen in the sample is liberated, moreover, the aqueous solution of chemicals is rapidly exhausted and must be replaced after a few analyses. Because of the large amount of water vapour in the chamber in which the blood gases are liberatedas a consequence of the use of aqueous solutions-the gases must be dried before gas chromatography is performed, for otherwise the columns will be impaired by the vapour. Since a gas chromatograph is extremely sensitive to variations in gas flow and since the perviousness of the drying agent to gas will vary according to its water content of the former, the calibration of the apparatus will vary in an inadmissible fashion.

The object of the present invention is to avoid the above disadvantages and in other respects simplify the analysis of blood gases; the proceduce in accordance with the invention is eminently suitable for this purpose. The essential features of the method are that (i) the blood sample is centrifuged, (ii) at the same time it is heated to a temperature at which the blood gases are liberated, and (iii) a continuous current of gas is maintained through the centrifuge bowl.

In accordance with the invention the blood sample is injected against the inner surface of a rotating centrifuge bowl; this is raised to the required temperature at least at the places with which the blood comes into contact.

The apparatus in accordance with the invention has the following essential features: it contains a centrifuge bowl, a device for injection of a blood sample against the inner surface of the rotating bowl, devices for heating at least the part of the centrifuge drum with which the blood comes into contact, and devices for ensuring a continuous current of gas through the centrifuge bowl, the object being that this stream of gas will carry with it the blood gases liberated on injection and vaporization of the sample.

The invention will be explained in greater detail below with reference to the attached diagram showing, in side elevation, a device in accordance with the invention.

The apparatus that is illustrated by way of example consists of the following components: A housing for an electric motor with a vertical shaft 12. The

Patented Sept. 27, 1966 motor 11 drives a shallow centrifuge bowl 13 which is detachably mounted on the upper end of the shaft 12. The bowl has a fitting cover 14 with a central hole, which is closed by a lid 15. On the upper surface of the housing 10 and surrounding the shaft 12 is a ring bearing 16 of, for instance, Phosphor bronze. The bowl has a plane ground area on its under surface which runs on the ring bearing 16, so that when the bowl is rotating it is kept at a constant level. On the upper surface of the housing 10 and concentrically with the shaft 12 there are also two rings, which have concentric ridges; these ridges intermesh with corresponding ridges of two similar rings on the under surface of the centrifuge bowl 13 so that two labyrinth seals 18 and 19 are formed.

The rim of the centrifuge bowl 13 is bent over so as to form an annular channel 20, which opens downwards. When the bowl is placed on the shaft 12 in such a manner that the ground surface 17 on the under side of the bowl rests on the ring bearing 16, the annular channel 20 is completely isolated from the outside by the labyrinth seals 18 and 19. When the centrifuge is running, a heating medium such as water vapour or hot air is conducted to the channel 20 through a tube 21 and away from the channel through a tube 22. In this way the radial outer wall 23 of the centrifuge bowl will be heated.

The wall 24 forming the channel 20 is closed by means of a flange 25 which is at right angles to the axis of rotation. On the upper surface of the flange is placed a smooth ring 26, of for instance, Phosphor bronze or steel. Against this ring 26 a packing ring 27, for instance a carbon sealing ring, is pressed by means of a number of spring screws 28. Between the packing ring 27 and the inside of the centrifuge cover 14 is a bellows 29, which is connected to the packing ring 27 and the inside of the centrifuge cover 14 so as to form a gas-tight joint.

The lid 15 is fastened on the centrifuge cover 14 by screws 30 and a gas-tight seal between these is provided by a ring washer 31.

The lid 15 has an opening 32 in which is fitted a rubber membrane 33 designed to resist the gas pressure in the centrifuge when it is running, but which is also easily pierced by a syringe needle 34 for injecting the blood sample into the centrifuge chamber 13. The membrane 33 is set in an inclined position so that the blood sample can be sprayed against the wall 23 of the centrifuge bowl. On the floor of the bowl there are radial ridges 35, the purpose of which is to facilitate transport of the injected blood towards the wall 23. Near the top of the wall 23 the bowl is provided with a metal ring 36, which curves slightly inwards. The purpose of this ring is to prevent the blood sample flowing over the edge of the centrifuge bowl during centrifugation.

The lid 15 contains an inlet tube 38 and an outlet tube 37 for gas.

The device functions in the following manner:

The centrifuge bowl 13 is first placed on the upper end of the motor shaft 12 and a firm grip is ensured by means of the axial wedge 12A. The centrifuge bowl 13 should then rest with its ground surface 17 supported on the ring bearing 16 and the engagement of the labyrinth seals 18 and 19 is then ensured. The centrifuge cover 14 with the lid 15 then occupies an elevated position, in which it is clamped at the pillar 39, a slotted clamp 40 being held firmly around the pillar 39 by a locking device 41. The locking device 41 is then released, after which the centrifuge cover 14 with the lid 15 are moved downwards so that the packing 27 rests against the ring 26. The motor 11 is then set running by means of the switch 42 on the housing 10. The centrifuge bowl 13 is then set in rotation. In connection with this operation the supply of heating medium is connected by means of a valve (not shown) through the tube 21, so that the heating medium flows through the tube 21 and the annular channel 20, to flow out by way of the tube 22. In the process the outer wall 23 of the centrifuge bowl will be heated to a temperature which is high enough to ensure liberation of the gases in the blood sample. A valve is then opened to admit a suitable gas, such as helium, through the supply tube 37; the interior of the centrifuge then fills with the gas, which flows out through the tube 38. The apparatu is now ready for injection of the blood sample.

The blood sample, of about 0.1 ml., the volume of which has been accurately determined, is injected through the membrane 33 which is pierced by the syringe needle 34. In this operation the needle 34 should be directed against the outer wall 23 of the centrifuge bowl which is heated in the manner described above. If a small part of the injected blood sample should reach the floor of the centrifuge bowl 13 the radial ridges 35 ensure that it is immediately set in rotation so that it will be thrown out towards the outer wall 23 by the centrifugal force. Because the blood comes into contact with the comparatively large wall surface which has been heated to the required temperature, the vaporizable part of the injected blood sample will be immediately vaporized; the blood gases will pass off through the outlet tube 37 together with the stream af gas passing through the centrifuge. All constituents of the injected blood sample that cannot be vaporized will, of course, be thrown out to the periphery of the bowl 13 where they will be retained without any risk of them being carried in the gas stream through the outlet tube 37. There will clearly be no large quantities of water vapour and hence no need to dry the sample of blood gases, and therefore all forms of drying tower and suchlike are avoided.

By virtue of the fact that the blood sample comes into contact with the large heated surface so that it is immediately vaporized in its entirety, an extremely well-defined reading on the analysis apparatus is obtained so that the evaluation of the reading with respect to the quantity of gas analysed on each occasion is facilitated.

No chemicals are required in the procedure according to the invention and the centrifuge bowl 13 is easily cleaned after a number of analyses have been performed. If required, a number of similar bowls might be used in succession.

A number of modifications and alterations in detail may be made within the framework of the principal idea covered by the invention.

What I claim is:

An apparatus for analyzing a sample of a vaporizable material for gases contained therein, comprising a housing, a motor mounted in said housing having a vertical shaft extending upwardly through said housing, a centrifuge bowl removably mounted on the upper end of said vertical shaft above the housing, said bowl being a shallow bowl having a rim which is turned over and extends downwardly to define an annular channel in the under surface of the bowl, said annular channel opening downwardly toward said housing, a bearing on said housing on which said bowl rotates, sealing means between the bottom of said bowl and said housing and comprising a first seal radially outwardly of said annular channel and a second seal radially inwardly of said annular channel, a system of tubes opening into said annular channel through said housing at points opposite said annular channel for conducting a heating medium to and from said annular channel, a cover above said bowl, a gas seal means extending between the inside surface of said cover and the periphery of said bowl andpermitting relative rotation between the cover and the bowl, means extending through said cover for projecting a sample into the bowl against the inside surface of the bowl, a gas inlet opening through said cover into the radially inner portion of said bowl and a gas outlet means opening out through the cover from the radially outer portion of said bowl for picking up gases vaporized when a sample is centrifuged and heated, a fixed pillar on said housing, and clamping means vertically movable on said pillar and on which said cover is mounted.

References Cited by the Examiner UNITED STATES PATENTS 315,398 4/1885 Eyre 2332 315,876 4/1885 Zimmer 233l3 X 399,113 3/1889 Adams et al 233l3 X 442,461 12/ 1 890 Sharples 23311 529,663 11/1894 Naylor 233l3 831,813 9/1906 Weber 23311 X 1,070,128 8/1913 Gross 22033 1,580,380 4/1925 MacDonald 400 2,160,433 5/1939 Grifiin et al. 2,182,159 12/1939 Miller et al. 233-11 2,216,542 10/1940 Paige 5552 X 2,274,658 3/1942 Booth 55--53 X 2,546,068 3/1951 Gustavsson 233l3 X 2,822,126 2/1958 Cohn 233--14 X 2,822,315 2/1958 Cohn 233l3 X 2,870,934 1/ 1959 Hill 220 -33 2,921,969 1/1960 Loy 23311 X 3,013,005 12/1961 Solvik 233l3 X 3,092,180 6/1963 Dahl-gren 159-6 X 3,096,283 7/1963 Hein. 3,148,146 9/1964 Asnes et al 23311 REUBEN FRIEDMAN, Primary Examiner.

D, TALBERT, JR., Assistant Examiner. 

